I'm not big on FE's (my favorite engine is the 429) but I would say that they are the same. The 390 is probably stroked and bored to 406. I could be wrong though, so try not to take my word for it.
The 406 is an FE. Has the 428's bore and the 390 stroke. Don't know it's the 390 block or not. Always heard the I know the 352 and 390 are the same, and I believe the 410. but I had always heard the 428's were different. Don't know where the 406 fit's in all of this.
The 406 was a high performance FE circa 1962/3. There were Hi Po 352s and 390s earlier but the 406 was the King of the Hill until the 427 came out in 1963.
All FEs are closely related, but I'm not sure if it's the same block. I don't think so. You can't bore out a 390 to a 428, even though they look very similar.
I thought the only diff. was the stroke between the 390 and the 428.The FE exchange rebuilding book says that they are all very similar,Different strokes,heads and manifolds.you can interchange alot . Dan
A 406 block externally looks a lot like a 390 block, however the cylinder walls are much thicker to allow overboring it to the larger size. A 390 block cannot be bored this far typically without weakening the block beyond repair.
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